In a radio communication system which supports services like multimedia broadcast multicast service (MBMS) which occupies many radio resources, a typical solution to save radio resources is to assign a dedicated frequency to the MBMS service.
MBMS service is of the broadcast nature, which may support far more users in a frequency than other services, for example an interactive service. But to services of other types, the capacity for the dedicated frequency is quite limited. So if user equipment in the dedicated frequency initiates a service of other type, the system will be unable to support and congestion will be caused. Thus, typically, the MSMS dedicated frequency only supports MBMS service, but does not support any non-MBMS services or supports non-MBMS services (for example data service) in a limited way.
According to associated 3GPP standards, before a MBMS service is initiated, the Universal Mobile Telecommunications System Terrestrial Radio Access Network (UTRAN) uses a Frequency Layer Convergence (FLC) technique to re-select user equipment (UE) interested in the MBMS service to the MBMS dedicated frequency.
Upon completion of the MBMS service, the UTRAN uses a Frequency Layer Dispersion (FLD) technique to disperse UE to another frequency (i.e. a normal frequency supporting any non-MBMS services) by sending a message indicating the frequency layer dispersion.
When a MBMS service is ongoing, since the MBMS dedicated frequency does not support any non-MBMS services (for example a voice call), UE can not perform a calling or called non-MBMS service in the MBMS dedicated frequency, wherein a calling service indicates that the non-MBMS service originates from the UE, while a called service indicates that the non-MBMS service terminates at the UE.